Semiconductor wafer inspection apparatus

ABSTRACT

A semiconductor wafer inspection apparatus is provided with a rotatable table on which a semiconductor wafer is held by suction, an illuminating device which illuminates at least an edge portion of the semiconductor wafer held on the rotatable table, an imaging device which captures an image of the edge portion of the semiconductor wafer when the edge portion is illuminated by the illuminating device, an image processing device which detects at least an edge cut amount or a crack by acquiring the image of the edge portion which is captured by the imaging device, and a display section which displays an image of the edge portion subjected to image processing by the image processing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Continuation application of U.S. application Ser. No.10/438,561, filed May 15, 2003, now U.S. Pat. No. 6,906,794, which is aContinuation Application of PCT Application No. PCT/JP02/09637, filedSep. 19, 2002, which was not published under PCT Article 21(2) inEnglish.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2001-285637, filed Sep. 19,2001; and No. 2002-154183, filed May 28, 2002, the entire contents ofboth of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor wafer inspectionapparatus which detects defects (including scratches, dust, and cracks)at the outer peripheral portion of a semiconductor wafer (hereinafterreferred to as a “wafer edge portion.”

2. Description of the Related Art

Normally, semiconductors are manufactured by executing steps describedbelow, and defect inspection is executed in each manufacturing step. Inthe pre-process of semiconductor device manufacture, an oxide film(SiO₂) is formed on the surface of a semiconductor wafer (hereinafterreferred to simply as a “wafer”), and then a thin silicon nitride filmis deposited on the oxide film.

Then, a photolithography step is carried out to form a thin film ofphotoresist (photosensitive resin) on the surface of the semiconductor.Subsequently, an adequate amount of rinsing liquid is dropped onto thewafer edge portion of the wafer, and the photoresist is removed from thewafer edge portion of the wafer by an amount corresponding to apredetermined width.

Then, processing using an exposure device, such as a stepper, isexecuted. That is, ultraviolet rays are guided to the photoresist-coatedwafer by way of a mask corresponding to a semiconductor circuit pattern,so that the semiconductor circuit pattern is transferred onto thephotoresist. Then, developing is executed. For example, the exposedphotoresist is dissolved in a solvent, thereby leaving the not exposedresist pattern.

Then, the oxide film and silicon nitride film formed on the surface ofthe wafer are successively subject to selective removal (etching), usingthe resist pattern remaining on the surface of the wafer as a mask. Theresist pattern is then removed from the surface of the wafer by ashing(resist separation). The resultant wafer is cleaned of impurities.

In the semiconductor manufacturing process described above, defectinspection is carried out in each manufacturing step. In the defectinspection, the surface of the semiconductor wafer is mainly inspectedto see if there are scratches, dust, cracks, stains or uneven portions.In recent years, the observation of the edge cut amount, thedistribution, etc. of the wafer is required. In particular, it should benoted that cracks result in the breaking of the wafer itself. This beingso, the presence or absence of cracks at the wafer edge portion has tobe detected as early a step as possible to determine whether the waferis good or bad.

A technique for inspecting a wafer edge portion is described, forexample, in Jpn. Pat. Appln. KOKAI Publication No. 9-269298. Accordingto this technique, a collimated beam condensed by an elliptic mirror isguided to the edge portion of a wafer. Of the diffracted light obtainedthereby, the low-order components are shielded so that the ellipticmirror condenses high-order components of the diffracted light. On thebasis of the intensity and/or the frequency components of the diffractedlight, a defect at the wafer edge portion or the property of the waferedge portion is identified. A technique for allowing a focal position tobe located inside a wafer and enabling detection of diffused lightcoming from inside the wafer, is also known in the art, as seen in Jpn.Pat. Appln. KOKAI Publication No. 2000-46537. Furthermore, a techniquefor irradiating the edge portion of a wafer with an infrared laser beamand examining the wafer by means of at least one video camera byslanting the wafer relative to the laser beam, is also known in the art,as seen in Jpn. Pat. Appln. KOKAI Publication No. 2000-136916.

Although the techniques described above enable detection of the edgeportion of a wafer, they in no way detect a defect at that wafer edgeportion, especially an edge cut line width. For this reason, theprocessing in the steps that follow the formation of a thin photoresistfilm may give rise to a defective wafer or other undesirable results.

For defect inspection, image data (an edge image) on the entire outercircumference of a wafer has to be acquired. In the above technologies,however, the edge image of the entire circumference is not acquired, andthe entire circumference of the wafer edge portion of a semiconductorwafer is not examined for defect detection.

An object of the present invention is to provide a semiconductor waferinspection apparatus which can easily inspect the outer circumference ofa semiconductor wafer in a short time in a semiconductor manufactureinspection process.

BRIEF SUMMARY OF THE INVENTION

A semiconductor wafer inspection apparatus of the present inventioncomprises: a rotatable table on which a semiconductor wafer is suckedand held; an illuminating device which illuminates at least the edgeportion of the semiconductor wafer held on the rotatable table; animaging device which captures an image of the edge portion of thesemiconductor wafer when the edge portion is illuminated by theilluminating device; an image processing device which detects at leastan edge cut amount or a crack by acquiring the image of the edge portioncaptured by the imaging device; and a display section which displays animage of the edge portion subjected to image processing by the imageprocessing device.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 shows the structure of an aligner to which a semiconductor waferinspection apparatus according to the first embodiment of the presentinvention is applied.

FIG. 2 is a schematic illustration showing the structure of a defectinspection apparatus main body according to the first embodiment of thepresent invention.

FIG. 3 illustrates how the semiconductor wafer inspection apparatus ofthe first embodiment of the present invention operates.

FIGS. 4A and 4B show an example of how a wafer edge portion is displayedin an enlarged scale in the first embodiment of the present invention.

FIG. 5 shows an example displaying a wafer edge portion related to thefirst embodiment of the present invention.

FIG. 6 is a schematic illustration showing the structure of a wafer edgeinspection apparatus according to the second embodiment of the presentinvention.

FIG. 7 shows an example of how belt-like image data is displayed in thewafer edge inspection apparatus of the second embodiment of the presentinvention.

FIG. 8 shows an example of how a defective portion image is displayed inan enlarged scale in the second embodiment of the present invention.

FIG. 9 is a schematic diagram showing coordinate positions and areas ofdefective portions, which are calculated by a defect detector accordingto the second embodiment of the present invention.

FIG. 10 shows the structure of an edge defect inspection apparatusaccording to the third embodiment of the present invention.

FIG. 11 shows a modification of how the belt-like image data isdisplayed in the wafer edge inspection apparatus of the third embodimentof the present invention.

FIG. 12 shows a modification of how the belt-like image data isdisplayed in the wafer edge inspection apparatus of the third embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 shows the structure of an aligner to which a semiconductor waferinspection apparatus according to a first embodiment of the presentinvention is applied. The aligner 1 has a function of aligningsemiconductor wafers 2 (hereinafter referred to simply as “wafers”)before they are transferred to a defect inspection apparatus main body3. The defect inspection apparatus main body 3 receives thesemiconductor wafers in the aligned state, and inspects the surface orthe rear surface of the semiconductor wafers 2 in either a macro fashionor a micro fashion to find various kinds of defects on them.

Two cassettes 4 and 5 are provided to store unexamined wafers 2 andexamined wafers 2. A transportation robot 6 is provided between thealigner 1 and the cassettes 4 and 5. The transportation robot 6 servesas a loader section configured to transport wafers 2 from the cassette 4to the defect inspection apparatus main body 3 by way of the aligner 1.

The transportation robot 6 is provided with two extendable/retractablearms 7 and 8, which are vertically arranged. Hands 9 and 10 are attachedto the arms 7 and 8, respectively. Since the hands 9 and 10 overlap eachother, they are depicted as one hand. The transportation robot 6 isprovided for a driving mechanism 11.

The driving mechanism 11 has a rail extending in parallel to thedirection in which the cassettes 4 and 5 are arranged side by side. Thedriving mechanism 11 drives the transportation robot 6 in the directionindicated by arrow a and brings it to a halt at positions correspondingto the cassettes 4 and 5.

When a wafer 2 is set on the rotatable table 1 a, the aligner 1 rotatesthe wafer 2 at a constant rotating speed and detects the center positionof the wafer 2 and the direction in which a notch or an orientation flatis present. Based on the result of this detection, the wafer 2 isaligned.

FIG. 2 is a schematic illustration showing the structure of a defectinspection apparatus main body 3 according to the first embodiment ofthe present invention.

Referring to FIG. 2, a 2-axis movement stage 30 (i.e., an electricstage), which is movable in both an X-axis direction and a Y-axisdirection, is made up of a Y-direction movement stage 31 a and anX-direction movement stage 32 a. The Y-direction movement stage 31 a isdriven in the Y direction by a Y-direction driving section 31; likewise,the X-direction movement stage 32 a is driven in the X direction by anX-direction driving section 32. A rotatable table 21 is located abovethe 2-axis movement stage 30. The rotatable table 21 holds a waferthereon by suction and is rotated by a rotation mechanism-drivingsection 20.

In a micro observation mode, an imaging device 100 captures image datathrough the use of an objective lens 60 of a microscope. When the edgeportion of a wafer is inspected, an edge observation mode is set. Inthis mode, the Y-direction movement stage 31 a and the X-directionmovement stage 32 a are controlled in such a manner that the edgeportion of the wafer sucked and held on the rotatable table 21 comes tothe position under the objective lens 60. After the wafer edge portionis adjusted to the position under the objective lens in this manner, theimaging device 100 begins to capture image data. An image of the waferedge portion obtained with the imaging device 100 is sent to an imageprocessing section where it is subjected to numerical analysis for thecalculation of an edge cut amount.

The semiconductor wafer inspection apparatus is operated using the GUI(graphic user interface) shown on an operation panel or the displaysection of a computer.

An “edge observation”/“ordinary observation” switching device 40 is aswitch that allows switching between the rotation mechanism-drivingsection 20 and the Y-direction driving section 31, which are to becontrolled by a pointing device 50. The pointing device 50 is a joystick (JS), for example. The pointing device 50 controls the position ofthe 2-axis movement stage 30. The pointing device 50 can also controlthe rotatable table 21 to determine the rotating direction and speed ofthe wafer. With this configuration, during the observation of the edgeportion (outer circumference) of a wafer, fine adjustment can be made tothe wafer position so that the edge portion of the wafer can be locatedat the position under the objective lens 60, and fine adjustment can bemade to the rotating speed to adjust the observation speed.

A description will now be given as to how the semiconductor waferinspection apparatus of the above structure operates.

FIG. 3 illustrates how the semiconductor wafer inspection apparatus ofthe first embodiment of the present invention operates. In thedescription below, reference will be made to the case where the operatorfirst performs ordinary defect inspection of a wafer surface and thenperforms inspection of a wafer edge portion. First of all, in step S1,the operator depresses an edge moving button provided for the operationpanel or an edge position moving button displayed on a screen of adisplay device. An edge position moving button, a rotation button, arotation stop button, a rotation/movement speed switching button, apointing device, and other operation buttons are displayed on a displaydevice. When one of the operation buttons is depressed, thecorresponding operation is performed.

When the edge position moving button is depressed, for example, theX-direction movement stage 32 a of the 2-axis movement stage 30 moves inthe X direction. As a result, the wafer sucked and held on the rotatabletable 21 moves until the edge portion comes to the position under theobjective lens 60 in step S2, thereby enabling observation of a detailedimage of the wafer edge portion and its neighboring portion. If focusingof the objective lens 60 is executed with the auto focus functionenabled during the observation of the wafer edge portion, the wafer edgemay move out of the range of the objective lens 60, making the focusingimpossible. To prevent this problem, it is preferable to disable theauto focus function during the observation of the wafer edge portion.When the wafer edge portion comes to the position under the objectivelens 60, a completion signal is sent from the stage in step S3, and amessage indicating this is displayed on the operation screen oroperation panel. Then, the operator confirms the image shown on thedisplay device in step S4, operates the pointing device 50, as needed,in step S5, and makes fine adjustment to the 2-axis movement stage 30 instep S6 so that the wafer edge portion entirely comes within the fieldof view of the objective lens. Thereafter, a completion signal isreturned from the Y-direction driving section 31 and the X-directiondriving section 32 in step S7, and the operator confirms the image shownon the display device in step 8.

Then, the operator selects the rotating direction by depressing therotation button in step S9. In response to this selection, rotationmechanism-driving section 20 is driven in step S10, and the wafer 2 onthe rotatable state 21 begins to rotate. In response to the rotation ofthe rotatable stage 21, a rotation start signal is returned from therotation mechanism-driving section 20 to the operation screen oroperation panel in step S11. The rotatable table 21 keeps rotating untilthe operator depresses the rotation stop button. In response to therotation of the rotatable table 21, the imaging device 100 captures animage of the edge portion of the wafer 2 located under the objectivelens 60 and the display device displays the captured image. In step S12,the operator observes an image of the wafer edge portion displayed onthe display device. When the wafer 2 has started rotating or in responseto the instruction by the operator, the “edge observation”/“ordinaryobservation” switching device 40 b is operated to select the edgeobservation mode. In this mode, the rotating speed of the rotatabletable 21 can be adjusted by means of the pointing device 50.

Thus, before the observation of the wafer edge portion, the position ofthe 2-axis movement stage 30 can be controlled by means of the pointingdevice 50 in such a manner that the observation target of the wafer edgeportion comes to the center of the field of view of the objective lens60. After the start of the observation of the wafer edge portion, therotating speed of the rotatable table 21 can be controlled by means ofthe pointing device 50 so that the observation speed becomes optimal tothe operator. This control significantly enhances the usability.

When the operator depresses the rotation stop button in step S13 at theend of the observation of the wafer edge portion, a stop signal issupplied to the rotation mechanism-driving section 20 to stop therotation of the rotatable table 21 (the rotation of the wafer).Thereafter, in step S15, a rotation stop signal is returned from therotation mechanism-driving section 20. The operator determines whetherto rotate the wafer 2 or to stop it. When the operator finds anundesirable rinse cut amount or a defective portion such as a crack, theoperator can depress the rotation stop button to stop the rotation ofthe rotatable table 21 as the need arises. When-the table 21 stops, animage of the wafer edge portion is captured by means of the imagingdevice 100 and image data obtained thereby is analyzed by means of theimage processing section. When the wafer edge portion is being observed,image data on the portion being observed is acquired regularly (atpredetermined intervals). The image processing section analyzes therinse cut amount and defects, including the crack and wafer chipping(fragment), and calculates the number of defects, coordinate positions,and sizes of the defects.

An automatic defect classification software is installed in the imageprocessing section. If the rinse cut amount is out of a predeterminedvalue range, or if the defect is determined as a crack or waferchipping, the wafer 2 is determined as defective. If the imageprocessing section determined that the rinse cut amount is undesirable,the wafer 2 is returned to the resist film removing step. If the imageprocessing section determined that the defect is a crack, the wafer 2 isdisposed of since it may crack in subsequent steps.

When the operator determined to end the observation of the wafer edgeportion in step S16, the operator depresses the reset button in stepS17. In response to the depression of the reset button, the rotationmechanism-driving section 20 is controlled in step S18, and therotatable table 21 is returned to the angular position it takes beforeobservation (an initial state). To be more specific, the angularposition (rotating angle) of the wafer is returned to the originalposition so that the notch of the wafer 2 sucked and held on therotatable table 21 comes to the original reference position, e.g., theposition of 0°. Thereafter, in step S19, a completion signal is returnedfrom the stage, and in step S20, the operator confirms the imagedisplayed on the display device.

FIGS. 4A and 4B show an example of how a wafer edge portion is displayedin an enlarged scale. If an abnormal portion that is considered to be acrack, for example, shown in FIG. 4A, is found when the wafer edgeportion is observed by means of the small-magnification objective lens60, the objective lens is replaced with a large-magnification one, andenlarged observation is performed in the manner shown in FIG. 4B. Themagnification may be changed when the operator finds an abnormal portionduring the visual observation through the eyepiece of the microscope orwhen the automatic defect classification software determines an abnormalportion is contained in the image captured by the imaging device 100.

In the manner described above, the abnormal portion is inspected in anenlarged scale, using the large-magnification objective lens 60. It istherefore possible to easily determine whether the abnormal portion is adefect or not. For example, observation is performed using an objectivelens which has small-magnification up to 5× or so. In the case where anabnormal portion is found, the small-magnification objective lens isreplaced with an objective lens which has large-magnification of 10×,20×, 50× or 100× larger than the small-magnification, and detaileddefect inspection is performed, with the abnormal portion beingenlarged. In the case where the abnormal portion is determined to be adefect, the related defect data and the image data are preferablystored. The defect data and the image data may be used in subsequentinspection.

During observation of a wafer edge portion, the operator sometimes hasdifficulty in understanding which portion of the entire wafer he or sheis observing. As shown in FIG. 5, therefore, the coordinates and therotating angle of a portion being observed should preferably be detectedbased on pulse signals provided by the Y-direction driving section 31,X-direction driving section 32 and rotation mechanism-driving section20. By so doing, the operation screen (operation panel) 61 can displaywhich portion of the wafer 2 is being observed at the present time. Forexample, a wafer map 2′ is displayed on the operation screen, and anobservation point A is indicated on the wafer map 2′, as shown in FIG.5. In addition, defects detected by the image processing section may bedisplayed on the wafer map 2A′, with kinds of defect being indicated incolors. When an arbitrary defect position displayed is clicked with apointer, the defect designated with the pointer may be displayed as anenlarged image. The operation screen 61 shown in FIG. 5 displays notonly a wafer image at the observation point A but also the followingbuttons: a classification button 62 used for classifying the defectsaccording to kinds, a save button 63 used for saving defect images, anda registration button 64 used for registering defect data.

As described above, an alignment mechanism is provided, and thealignment mechanism includes three sensors for detecting a wafer edge.The sensors are on the concentric circle whose radius is the same as thewafer 2 and whose center is the center of rotation of the rotatabletable 21 which is disposed on the 2-axis movement stage 30. Thealignment mechanism detects how the center of the wafer is shifted onthe basis of the coordinate data on the three wafer edge points, andautomatically controls the 2-axis movement stage 30 in relation to therotation of the rotatable table 21 until the center of the wafer 2becomes the center of rotation. In this manner, even if thesemiconductor wafer 2 sucked and held on the rotatable table 21 isshifted from the right position, its position is corrected so that itscenter becomes the center of rotation. Hence, the wafer edge portion ofthe semiconductor wafer 2 and its neighboring portion can be accuratelyobserved at all times.

According to the first embodiment, a small-magnification objective lensis replaced with a large-magnification objective lens so as to enable adefective portion to be displayed in an enlarged scale and examined indetail.

It is not necessary to provide an inspection section specially designedfor the inspection of a wafer edge. That is, the edge of a wafer on therotatable table located under the objective lens of a microscope can beobserved by making use of the micro observation function of themicroscope.

Defects existing on the edge of the circumference of a semiconductorwafer, such as wafer chipping, cracks, and a rinse cut amount, can bedetected, and a defective wafer is prevented from being made in thephotolithography step executed after the application of photoresist.

Positional information on defects may be displayed on a wafer map, andthe kinds of defects may be indicated in different colors. By so doing,it is possible to visually recognize what kind of defect the wafer has,and where it is located.

The present invention is not limited to the first embodiment describedabove. In the above embodiment, at the start of the edge observation,the 2-axis movement stage moves a semiconductor wafer in the X-Y planeperpendicular to the optical axis direction of the micro observationoptical system, until the wafer edge portion comes to the position underthe objective lens. Instead of this configuration, the objective lensmay be moved to the position located above the wafer edge portion.

The aligner to which the semiconductor wafer inspection apparatus of thesecond embodiment is applied has a similar structure to that depicted inFIG. 1.

FIG. 6 is a schematic illustration showing the structure of a wafer edgeinspection apparatus according to the second embodiment of the presentinvention. The aligner 1 described above is provided with a wafer edgeinspection apparatus 70, such as that shown in FIG. 6. An illuminatingdevice 71 is located above the aligner 1. Illuminating light emittedfrom the illuminating device 71 falls on the wafer edge portion of awafer 2 at a predetermined angle (slantwise illumination). Theilluminating angle θ1 of the illuminating device 71 can be set at anarbitrary angle when the illuminating light illuminates the wafer edgeportion of the wafer 2 slantwise.

A filter changer 72 is provided in the optical path of the illuminatinglight emitted from the illuminating device 71. By use of this filterchanger 72, either a band-pass filter 731 or a polarizing filter 732 isinserted in the optical path of the illuminating light (removableinsertion). When the band-pass filter 731 is inserted in theilluminating optical path, illuminating light having designatedwavelengths travels to the wafer edge portion of the wafer 2, therebyenabling interference imaging. When the polarizing filter 732 isinserted in the illuminating path, polarizing imaging is enabled.

An imaging device 74 is disposed above the aligner 1 in such a mannerthat it is located on the side opposing the illuminating device 71. Theimaging device 74 captures images of the wafer edge portion of the wafer2 when this wafer 2 is rotated at a constant speed by the aligner 1. Theimaging device 74 is a one-dimensional CCD (a line sensor camera), atwo-dimensional CCD sensor, a time delay camera (a TDI camera), or thelike. The imaging device 74 is able to capture images at an arbitraryangle θ2 with respect to the wafer edge portion of the wafer 2. Thescaling factor of the imaging device 74 can be arbitrarily determined,thereby enabling selection of an appropriate vertical resolution. Let usassume that the imaging device 74 is a one-dimensional CCD and is usedfor continuously capturing images of the wafer edge portion of the wafer2 rotating at a constant speed in synchronism with the rotating speed ofthe rotatable table 1 a of the aligner 1. In this case, the wafer edgeportion is acquired as belt-like image data. Therefore, the horizontalimaging resolution of the imaging device 74 (i.e., the longitudinalresolution of the wafer edge portion) can be varied by changing therotating speed of the rotatable table 1 a.

When the imaging device 74 is moved closer to the wafer 2, the scalingfactor increases. Image signals output from the imaging device 74 aresupplied to an edge defect processing section 75. The edge defectprocessing section 75 compares the belt-like image data acquired by theimaging device 74 with image data on a wafer of good quality. Based onthis comparison, the edge defect processing section 75 detects adefective portion at the wafer edge portion and displays the relatedbelt-like image data.

To be more specific, the edge defect processing section 75 comprises thefollowing: a main controller 76 such as a CPU; an image memory 77 forwhich data reading and data writing are enabled under the control of themain controller 76 and which stores image signals from the imagingdevice 74 as belt-like image data; a good-quality-image data memory 78which stores image data on the wafer edge portion of a wafer of goodquality; a defect detecting section 79 which compares the belt-likeimage data with the image data on the wafer 2 of good quality anddetects a defective portion at the wafer edge portion of the wafer 2;and a display section 81 which causes the belt-like image data to bedisplayed on a display 80.

The image data on the semiconductor wafer 2 of good quality, which isstored in the good-quality-image data memory 78, is belt-like image dataobtained with respect to a wafer 2 which is considered to be a good onein previous inspection. Alternatively, the wafers 2 of one lot aresequentially inspected, and each time a wafer 2 of good quality isdetermined, the image data of that wafer 2 is used as updating data.

The defect detecting section 79 compares the belt-like image data withimage data on a wafer 2 of good quality. Based on the comparison, thedefect detecting section 79 determines the kinds of defects at the waferedge portion of a wafer 2, such as dust, scratches, wafer chipping,cracks, etc., and calculates the number of defects the wafer 2 has, thecoordinate positions (X, Y) of the defects, and the areas (sizes) of thedefects.

The defect detection section 79 detects an edge cut line width afterphotoresist is coated on the surface of the wafer 2 in the semiconductormanufacturing process. The edge cut line width is a width by which thephotoresist is cut out after dropping a rinse liquid on the wafer edgeportion of the wafer 2. The detected edge cut line width is comparedwith a predetermined threshold value to determine if the edge cut linewidth is within a normal range. If abnormality is detected, the defectdetecting section 79 calculates the coordinate positions (X, Y) andareas.

FIG. 7 shows an example of how belt-like image data is displayed in thewafer edge inspection apparatus. The display section 81 dividesbelt-like image data into a plurality of pieces, for example four imagedata pieces A, B, C and D corresponding to 90° of the wafer 2, as shownin FIG. 7. These image data pieces A, B, C and D are displayed on thedisplay 80.

G1 denotes chipping in image data piece A, G2 denotes a scratch in imagedata piece B, G3 denotes a dust particle in image data piece C, and G4denotes an abnormal portion of an edge cut line width in image datapiece D,.

The display section 81 has a function of laying out the belt-like imagedata obtained by the line sensor camera on the screen of a wafer map insuch a manner that it forms a circular shape and displaying it on thedisplay 80, as shown in FIG. 7. In this image processing, the four imagedata pieces A, B, C and D form one circular image.

When one of the defective portions G1–G4 is clicked after moving apointer thereto on the wafer map displayed on the display 80, thedisplay section 81 causes an enlarged image of the correspondingdefective portion to be displayed on the display 80, as shown in FIG. 8.

The display section 81 has a function of classifying and displaying thedefective portions G1 to G4 in different colors according to theirkinds, when the belt-like image data (image data pieces A, B, C and D)is displayed on the display 80.

The display section 81 displays not only belt-like image data (imagedata pieces A, B, C and D) but also results of determination made by thedefect detecting section 79. Examples of defects at the wafer edgeportion of the semiconductor wafer 2 include a scratch, dust, chipping(wafer chipping), an abnormal edge cut line width, crack, etc., andexamples of the results of determination include coordinate positions(X, Y) of the defects, areas of them, etc.

A description will now be given as to how the wafer edge inspectionapparatus of the above configuration operates.

When a wafer 2 is set, the aligner 1 rotates the wafer 2 at a constantrotating speed, and detects the coordinates of three points on the edgeof the wafer 2 by a edge sensor. Based on the edge coordinate data onpoints, the center position of the wafer 2 and the direction of thenotch are detected. The semiconductor wafer 2 is aligned on the basis ofthe results of detection.

Simultaneous with this, the illuminating device 71 illuminates the waferedge portion of the semiconductor wafer 2 rotating at a constant speed.The illumination angle is θ1.

The imaging device 74 captures images of the light reflected by thewafer edge portion of the wafer 2 rotated by the aligner 1 at a constantrotating speed. The images are captured at arbitrary angle θ2, which isdetermined relative to the wafer edge portion of the wafer 2. The imagesignals are output and stored in the image memory 77 of the edge defectprocessing section 75 as belt-like image data on the wafer edge portionof the wafer.

The defect detecting section 79 of the edge defect processing section 75compares the captured image data with image data on a good-qualitywafer. Based on this comparison, the defect detecting section 79calculates the coordinate positions (X, Y) and areas of the defects atthe wafer edge portion, such as dust, a scratch, chipping (waferchipping), a crack, an abnormal edge cut line width, etc.

The display section 81 divides the captured belt-like image data storedin the image memory 77 into pieces, as shown in FIG. 7. For example,four image data pieces A, B, C and D are prepared (all four pieces areconsidered to constitute a circle, so that each of the four piecescorresponds to 90°, for example) These divided image data pieces A, B, Cand D are displayed on the display 80. Simultaneous with this, thedisplay section 81 lays out the belt-like image data in such a mannerthat the laid-out image data forms a circle in conformity with thecircular shape of the semiconductor wafer 2. The resultant circularimage data is shown on the display 80.

As shown in FIG. 7, the circular image data is displayed in the upperportion of the screen of the display 80, and the four belt-like imagedata pieces A, B, C and D are displayed in the lower portion so thatthey are arranged in the vertical direction. Reference symbols G1 to G4are indicated in both the circular image and the belt-like dividedimages (G1: chipping, G2: scratch, G3: dust, G4: abnormal portion ofedge cut line width).

In the screen portion of the display 80 where the belt-like image data(image data pieces A, B, C and D) is displayed, the display section 81shows the defective portions G1 to G4 in different colors according totheir kinds.

The display section 81 displays not only belt-like image data (imagedata pieces A, B, C and D) but also results of determination made by thedefect detecting section 79. Examples of defects at the wafer edgeportion of the wafer 2 include a scratch, dust, chipping (waferchipping), an abnormal edge cut line width, crack, etc., and examples ofthe results of determination include coordinate positions (X, Y) of thedefects, areas of them, etc.

In the second embodiment described above, the imaging device 74 capturesimages of the wafer edge portion of the wafer 2 when this wafer 2 isrotated at a constant speed by the aligner 1. The captured belt-likeimage data is compared with image data on a good-quality wafer, for thedefect inspection of the wafer edge portion of the semiconductor wafer2. Simultaneous with this defect inspection, the belt-like image data isdisplayed as divided image data pieces A, B, C and D, and as circularlylaid-out image data. Therefore, defects at the wafer edge portion of thecircumference of the semiconductor wafer 1 can be detected, includingdust, a scratch, chipping (wafer chipping), a crack, and an abnormalportion of an edge cut line width.

Because of the defect detection described above, one of the causes ofdefective wafers being manufactured can be reliably detected when theprocessing of the steps that follows the application of a thinphotoresist film is executed. In addition, since the horizontal imagingresolution can be varied by changing the rotating speed of the aligner1, the resolution in the longitudinal direction of the wafer edgeportion can be improved. As a result, distortion-free image data can beacquired, and defects can be detected with high accuracy.

When the aligner 1 performs an alignment operation to transport a wafer2 to the defect inspection apparatus main body 3, the aligner 1 rotatesthat wafer 2 at a constant speed. This rotation is utilized in thedefect inspection performed for the wafer edge portion of the wafer 2.Therefore, the inspection of a wafer edge can be performed withoutemploying a dedicated inspection apparatus, and what is required is asimple structure wherein the illuminating device 71, the imaging device74 and the edge defect processing section 75 are merely added to theexisting aligner 1.

Furthermore, both the belt-like image data and the circularly laid-outimage data are displayed. Thanks to this feature, it is possible tovisually recognize where defects G1 to G4 (e.g., dust, a scratch, waferchipping, a crack, an abnormal portion of a edge cut line width) arelocated on the actual semiconductor wafer 2.

Information on the wafer 2, such as a wafer identification number W (awafer ID), is attached to the wafer edge portion of the semiconductorwafer 2. The identification number W is attached at the predeterminedposition on the wafer edge portion. The identification number W ischaracter information “AEO21”, for example.

To recognize the identification number W, the image device 74 is movedto the position where the identification number W is attached. Imagesignals output from the imaging device 74 are subjected to imageprocessing executed by an information reading section 82 additionallyprovided for the edge defect processing section 75 shown in FIG. 6.Based on this image processing, the identification number of thesemiconductor wafer 2 attached to the wafer edge portion is recognizedas characters or letters.

There may be a case where the wafer edge portion of the semiconductorwafer 2 is covered with a thin film. In this case, the identificationnumber W of the semiconductor wafer 2 is not recognized as characters orletters. To solve this problem, a filter having a predeterminedwavelength is provided for either the illuminating device 71 or theimaging device 74. The filter enables the identification number W to berecognized as characters or letters, despite the thin film covering thewafer wedge portion of the semiconductor wafer 2.

Defects may be displayed together with reference symbols G1 to G4attached thereto or in different colors according to their kinds. Wherethe defects are displayed in this manner, the positions and kinds of thedefects can be correctly identified.

The actual image processing required for displaying the circularly laidout image data is simply a matter of pasting the four image data piecesA, B, C and D to one another. In other words, no complicated imageprocessing is needed.

As the defects G1 to G4 on the wafer edge portion of the semiconductorwafer 2, dust, a scratch, wafer chipping, a crack, an abnormal portionof a edge cut line width etc. are displayed, and they are displayedtogether with their coordinate positions (X, Y) and areas. This enableseasy understanding of the states of the defects G1 to G4. In addition,the defects G1 to G4 can be inspected in detail by displaying enlargedimages of them on the screen of the display 80.

Observation based on interference imaging can be performed by insertingthe band-pass filter 731 in the illumination path by means of the filterchanger 72. Likewise, observation based on polarized imaging can beperformed by inserting the polarizing filter 732 in the illuminationpath by means of the filter changer 72.

FIG. 10 shows the structure of an edge defect inspection apparatusaccording to the third embodiment of the present invention. The edgedefect inspection apparatus 100 is featured by employing an incidenttelecentric illuminating/image formation optical system. A sensor casing101 is tubular.

The light source is a light emitting diode (LED) 102. The LED 102 emitsLED light and is provided on the side face of the sensor casing 101.

A half mirror 103 is provided slantwise inside the sensor casing 101.The half mirror 103 is an optical path-splitting element. It reflectsthe LED light emitted from the LED 102 so that the reflected LED lighttravels toward a telecentric lens 104. It also allows transmission ofreflected light reflected by a semiconductor wafer 2 and condensed bythe telecentric lens 104.

The telecentric lens 104 functions as a collimating lens for collimatingthe LED light emitted from the LED 102 and irradiating the wafer edgeportion of the semiconductor wafer 2 with the collimated LED light. Thetelecentric lens 104 also functions as a focusing lens for focusing theLED light reflected by the semiconductor wafer 2.

An image sensor 106 is on the optical axis P of the telecentric lens 104and located on the rear focus side of the lens 104. The image sensor 106includes a diaphragm 107, a relay image formation lens 108 and atwo-dimensional imaging element 109.

The two-dimensional imaging element 109 includes a plurality ofsolid-state imaging elements (CCD) that are arranged in rows and columnsin a two-dimensional plane. The image sensor 106 functions as a linesensor camera by using image data which are included in two-dimensionalimage signals acquired by the two dimensional imaging element 109 andwhich correspond to one line or a number of lines.

The edge defect inspection apparatus 100 is located above the wafer edgeportion of the wafer 2 at a position where it does not become anobstacle to the transportation or conveyance of the wafer 2. The edgedefect processing section 75 shown in FIG. 6 is connected to the outputterminal of the image sensor 106.

As in the second embodiment, the edge defect inspection apparatus 100 ofthe third embodiment captures images of the wafer edge portion of thesemiconductor wafer 2 rotating at a constant speed by the aligner 1. Insynchronism with the constant rotating speed of the aligner 1, thetwo-dimensional imaging element 109 of the image sensor 106 capturesimages of the wafer edge portion of the semiconductor wafer 2. As aresult, the belt-like image data of the wafer edge portion, such as thatshown in FIG. 7, is acquired. Since the image processing by the edgedefect processing section 75 is similar to the image processingperformed in the second embodiment, a detailed description of it will beomitted.

Like the second embodiment, the third embodiment acquires images of thewafer edge portion of the rotating wafer 2 with the image sensor 106,compares the resultant belt-like image data with image data on a goodproduct, and inspects the wafer edge portion of the semiconductor wafer2 on the basis of the comparison.

The third embodiment produces advantages similar to those of the secondembodiment. In addition, the LED 102, the telecentric lens 104 and theimage sensor 106 are arranged close to the half mirror 103, so that theedge defect inspection apparatus 100 is small as a whole. Hence, theedge defect inspection apparatus 100 can be easily applied to thealigner of a manufacturing apparatus, such as an inspection apparatuswhich performs surface defect detection or pattern shape measurementwith respect to a semiconductor wafer 2 supplied in a semiconductormanufacturing process, an exposure apparatus, or the like.

The present invention is not limited to the second or third embodiment.For example, data can be displayed on the screen of the display 80 in amodified manner, as described below.

FIGS. 11 and 12 show modifications of how belt-like image data isdisplayed in the wafer edge inspection apparatus. In the displayexamples shown in FIG. 11, image data pieces A, B, C and D are displayedalong the outer circumference of circularly laid-out image data. Inother words, the image data pieces A, B, C and D are displayed so thateach may correspond to 90° of the circular image data. In this manner,the positional relationships between the image data and the dividedimage data pieces are indicated.

In the display example shown in FIG. 12, image data pieces E and F aredisplayed above and under the circularly laid-out image data. In otherwords, the divided image data pieces E and F are displayed so that eachmay correspond to 180° of the circular image data. In this manner, thepositional relationships between the image data and the divided imagedata pieces are indicated. In the display example, the image data isdivided into two pieces E and F each corresponding to 180°. The anglebased on which the circular image data is divided can be determinedarbittarily.

When an enlarged image of a defect (e.g., defect G1) is displayed inresponse to a click operation by the operator, a zoom function may beutilized. That is, the scaling factor may be changed continuously. Inaddition, the positions of defects G1 to G4 may be detected using thenotch N or orientation flat of the semiconductor wafer 2 as a referenceposition. In this case, the positions of defects G1 to G4 are calculatedand displayed as angles determined in relation to that referenceposition. Further, part of the belt-like image data is displayed on thedisplay 80, and the displayed area may be varied in response to theoperator's operation, for scroll display.

The semiconductor wafer apparatus can be provided for various types ofmanufacturing apparatuses which rotate wafers 2 at a constant speed.Needless to say, the present invention is not limited to the field ofmanufacturing semiconductor devices; it may be applied to any type ofapparatus that is used for inspection or observation of the outercircumference of a circular object.

The present invention is not limited to the embodiments described above,and may be modified in various ways without departing from the spiritand scope of the invention.

According to the present invention, it is possible to provide asemiconductor wafer inspection apparatus that enables the outercircumference portion of a semiconductor wafer to be easily inspected ina short time in a semiconductor device manufacturing/inspecting step.

In other words, according to the present invention, the edge portion ofthe semiconductor wafer and its neighboring portions can be smoothlyobserved by use of a micro observation optical system. Therefore, thesemiconductor manufacturing apparatus can execute an inspection stepwith high efficiency. In addition, since the edge portion can beobserved easily and a smooth operation enabled, the productivity in thesemiconductor inspection process can be increased.

Furthermore, the present invention enables defect determination for thecircumference of the edge portion of the semiconductor wafer.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A semiconductor wafer inspection apparatus comprising: a rotatabletable on which a semiconductor wafer is held by suction; an illuminatingdevice which illuminates at least an edge portion of the semiconductorwafer held on the rotatable table; an imaging device, which is disposedat a same side as the illumination device with respect to a surface ofthe semiconductor wafer, and which captures an image of the edge portionof the semiconductor wafer by light from a surface of the edge portionwhen the edge portion is illuminated by the illuminating device; animage processing device which detects at least one of an edge cut linewidth and a crack on the surface of the edge portion by acquiring theimage of the edge portion which is captured by the imaging device; and adisplay section which displays an image of the edge portion subjected toimage processing by the image processing device; wherein the imageprocessing device determines that the semiconductor wafer is defectiveif the edge cut line width is outside of a predetermined value range,and calculates a position of the defective edge cut line width withrespect a position of a notch of the semiconductor wafer.
 2. Asemiconductor wafer inspection apparatus comprising: a rotatable tableon which a semiconductor wafer is held by suction; an illuminatingdevice which illuminates at least an edge portion of the semiconductorwafer held on the rotatable table; an imaging device, which is disposedat a same side as the illumination device with respect to a surface ofthe semiconductor wafer, and which captures an image of the edge portionof the semiconductor wafer by light from a surface of the edge portionwhen the edge portion is illuminated by the illuminating device; animage processing device which detects at least one of an edge cut linewidth and a crack on the surface of the edge portion by acquiring theimage of the edge portion which is captured by the imaging device; and adisplay section which displays an image of the edge portion subjected toimage processing by the image processing device; wherein the imageprocessing device carries out automatic defect classification toclassify at least a defect in the edge cut line width and a defect dueto the crack.
 3. A semiconductor wafer inspection apparatus comprising:a rotatable table on which a semiconductor wafer is held by suction; anilluminating device which illuminates at least an edge portion of thesemiconductor wafer held on the rotatable table; an imagine device,which is disposed at a same side as the illumination device with respectto a surface of the semiconductor wafer, and which captures an image ofthe edge portion of the semiconductor wafer by light from a surface ofthe edge portion when the edge portion is illuminated by theilluminating device; an image processing device which detects at leastone of an edge cut line width and a crack on the surface of the edgeportion by acquiring the image of the edge portion which is captured bythe imaging device; and a display section which displays an image of theedge portion subjected to image processing by the image processingdevice; wherein the imaging device includes an objective lens whichenlarges an image of the edge portion of the semiconductor wafer at apredetermined magnification, the rotatable table is disposed on a 2-axismovement stage which moves the edge portion of the semiconductor waferto a position under the objective lens, and the imaging device capturesan image of the edge portion of the semiconductor wafer, with therotatable table kept rotating.
 4. A semiconductor wafer inspectionapparatus according to claim 3, wherein the 2-axis movement stage ismoved in X and Y directions such that a center of the semiconductorwafer, which is predetermined in relation to a rotation of the rotatabletable, becomes a center of rotation.
 5. A semiconductor wafer inspectionapparatus according to claim 3, wherein the 2-axis movement stage ismoved in X and Y directions based on a center shift amount of thesemiconductor wafer, which is predetermined in relation to a rotation ofthe rotatable table, such that the edge portion of the semiconductorwafer is within a field of view of the objective lens at all times.
 6. Asemiconductor wafer inspection apparatus according to claim 3, whereinthe 2-axis movement stage is slightly moved in the X and Y directions byuse of a pointing device until the edge portion comes to a center of afield of view of the objective lens.
 7. A semiconductor wafer inspectionapparatus according to claim 3, wherein the rotatable table includescontrol means for controlling a rotating speed thereof.
 8. Asemiconductor wafer inspection apparatus comprising: a rotatable tableon which a semiconductor wafer is held by suction; an illuminatingdevice which illuminates at least an edge portion of the semiconductorwafer held on the rotatable table; an imaging device, which is disposedat a same side as the illumination device with respect to a surface ofthe semiconductor wafer, and which captures an image of the edge portionof the semiconductor wafer by light from a surface of the edge portionwhen the edge portion is illuminated by the illuminating device; animage processing device which detects at least one of an edge cut linewidth and a crack on the surface of the edge portion by acquiring theimage of the edge portion which is captured by the imaging device; and adisplay section which displays an image of the edge portion subjected toimage processing by the image processing device; wherein the imagingdevice and the illuminating device are inclined at a predetermined anglewith respect to a surface of the semiconductor wafer, and anilluminating angle of the illuminating device is variable.